1. Field of the Disclosure
Embodiments of the present invention relate to an organic light emitting display device using an encapsulation substrate.
2. Discussion of the Related Art
With the advancement of an information-oriented society, attention is being focused on technology for realizing a display device using an organic light emitting diode (OLED) which emits light in itself among various display devices. In contrast to a related art liquid crystal display device or plasma display device, the organic light emitting diode (OLED) has various advantages such as more rapid response speed, better light emitting efficiency and luminance, wider viewing angle and etc.
In a case of the display device using the organic light emitting diode (hereinafter, referred to as ‘organic light emitting display device’), a plurality of pixels are arranged in a matrix configuration, wherein each pixel includes an organic light emitting diode, and a brightness in the pixels selected by a scan signal is controlled in accordance with a grayscale of data. Especially, since the organic light emitting display device emits light in itself, it is possible to realize high contrast ratio, ultra-thinness, dynamic image by a rapid response speed of several micro seconds (μs), and wide viewing angle. In addition, the organic light emitting display device is stably driven by a low voltage even at a low temperature so that it is possible to facilitate design and manufacturing process of a driving circuit. Also, a method for manufacturing the organic light emitting display device does not need a process for injecting liquid crystal of the related art liquid crystal display device. Furthermore, in case of the organic light emitting display device, a display panel is manufactured through a deposition of organic materials, and an encapsulation is used to protect the organic materials from moisture and oxygen.
FIG. 1A is a cross sectional view illustrating a related art organic light emitting display device. As shown in FIG. 1A, the related art organic light emitting display device includes an organic light emitting diode layer 30 formed between a first substrate 10 and a second substrate 20, whereby the related art organic light emitting display device displays an image by emitting light upwardly or downwardly.
FIG. 1B is a plane view illustrating the related art organic light emitting display device shown in FIG. 1A. As shown in FIG. 1B, a plurality of power lines are formed to apply power to each pixel (P), and the plurality of power lines are provided to apply various kinds (i.e., amounts) of power. Although not shown, the power line may extend to the inside of pixel so as to apply power needed to each pixel. For example, a high-potential voltage line (VL1) may extend on a first substrate 11 to the periphery of each pixel so as to apply a high-potential voltage, or a high-potential voltage line (VL3) may extend to the periphery of each pixel so as to apply a specific voltage. As shown in FIG. 1C, when a circuit formed in each pixel is designed to drive the organic light emitting diode layer only when the circuit is applied with various powers. The circuit includes a plurality of transistors including transistor T1, transistor T2, and transistor T3. The drain electrode of transistor T1 is connected to voltage supply VDD and the source of transistor T1 is connected to the anode of the organic light emitting diode (OLED) and the source of transistor T3. The gate of transistor T1 is connected to the drain of transistor T2. The source of transistor T2 is connected to Vdata. The drain of transistor T3 is connected to a reference voltage Vref. Furthermore, a capacitor (Cap) is connected between the gate and source of transistor T1.
Although not shown, after forming an organic light emitting material to apply a low-potential voltage on the first substrate 11, a cathode electrode layer may be formed to entirely cover an upper side of each pixel, or may be brought into contact with a side voltage line (VL2) at a side of the first substrate 11.
The high-potential voltage, low-potential voltage or specific voltage applied to the organic light emitting display device has to be maintained constantly without deviation, and transmitted to the plurality of pixels. However, according to a recent trend of a large-sized substrate, the voltage is not maintained constantly so that the deviation occurs in partial regions of the panel, that is, voltage drop (IR Drop) occurs.
The voltage drop might cause non-uniformity in the display characteristics of the panel of the organic light emitting display device. In severe cases, a product using the organic light emitting display device with the inferior display characteristics might be discarded.